Shipping payment through an account code instead

Is there a way by which a buyer can enter a FedEx/ UPS shipping code/ account details and not pay shipping, and Lulu charges that account instead of paying through its own account? If not, is there a place in Lulu where we can request this feature?

A couple of people showed interest in buying multiple copies of my book, but they are not allowed to pay for shipping; they can only use their account.